The present invention relates to devices for injecting, administering, infusing, dispensing or delivering a substance, and to methods of making and using such devices. More particularly, it relates to an administering device for administering a liquid agent, e.g., a medicinal or therapeutic substance or product, from a multi-chamber carpule or ampoule, e.g. a two-chamber carpule, multi-chamber container or reservoir, multi-chamber ampoule, etc.
Various agents, such as growth hormone for example, can not be stored for any length of time dissolved in a liquid. However, to provide successful treatment for growth hormone problems, for example, it is necessary to introduce such agents into a patient's body tissue in liquid form. Administering devices, e.g., injection pens, may be used for this purpose. To enable such substances with a short shelf-life to be made available in a liquid medium for administering with injection devices, multi-chamber carpules, e.g. two-chamber carpules or ampoules, have been developed, in which an agent in a dried or lyophilized form is stored in a first carpule chamber and a dissolving liquid is stored in a second carpule chamber separately from the agent. The two chambers are usually separated from one another by displaceable stoppers. The first chamber usually comprises an outlet of the carpule closed by a membrane, for example, the carpule wall and a first stopper. The second chamber usually adjoins the first chamber and is formed by the first stopper, the carpule wall and a second stopper. Along the longitudinal axis of the carpule and hence along the axis along which the stopper can be pushed, a bypass is provided in the carpule wall, which can be used as a bypass for the dissolving liquid around the first stopper. To mix the agent with the dissolving liquid, a pressure is applied to the second stopper inside the carpule, which is transmitted to the first stopper by the non-compressible dissolving liquid. The two stoppers are therefore moved along the longitudinal axis of the carpule relative to the carpule wall. As soon as the first stopper has moved so that it lies in the region of the carpule bypass, the dissolving liquid passes out from the second chamber through the bypass and into the first chamber containing the agent. The second carpule stopper can be pushed relative to the carpule wall and toward the first stopper until it lies against the first stopper. When the second stopper is pushed again, the first stopper is moved with it and the dissolving liquid together with the agent can be dispensed through the carpule opening. To this end, an injection needle is fitted on the carpule opening, which is able to establish a fluid connection to the first carpule chamber. When mixing the agent with the dissolving liquid, care must be taken to ensure that the agent is not exposed to excessive flows of dissolving liquid. Foaming should be avoided during mixing as far as possible. The agent is then ready in dissolved form and can be injected into the patient's tissue with conventional administering devices.
Patent specification DE 10 2004 055 298 A1 discloses a mixing device for a two-chamber carpule (or ampoule), in which a two-chamber carpule is accommodated in a mixing sleeve, and the mixing sleeve is fitted by an axial movement toward an administering device. According to the English abstract (available from the esp@cenet database), it further relates to a device for mixing injected medicine comprising an ampoule sleeve for receiving an ampoule with medicine, a mixing sleeve with a mixing path, an abutment and a guiding unit having a power transmission structure which converts a linear movement in the axial direction of the mixing device into a rotary movement. As the mixing sleeve is pushed on, the stoppers of the two-chamber carpule are moved inside the carpule and the agent is mixed with the dissolving liquid.
Patent specification EP 0 298 067 B1 (the English equivalent is U.S. Pat. No. 4,968,299) discloses an arrangement in which the carpule is inserted in a carpule sleeve and the carpule sleeve is screwed into the housing of an administering device. Due to the axial movement during the screwing-on operation, the stoppers are moved inside the two-chamber carpule and the agent is mixed with the dissolving liquid. The devices known from the prior art enable the agent to be mixed slowly to avoid foaming or prevent damage to the agent.
For users of these types of devices, however, it is difficult to tell when the mixing procedure is complete and the agent has therefore been fully dissolved in the dissolving liquid in the desired concentration. Before administering an agent in liquid form into a patient's tissue by an administering device, it is necessary to vent the liquid duct between the carpule chamber in which the liquid is contained and the tip of an injection needle. This operation may be thought of and/or referred to as priming. In the case of the administering operation which takes place using two-chamber carpules known from the prior art, the priming operation must be actively carried out by the user and may be, therefore, forgotten before administering a liquid agent.